This study investigated the contribution of different cannabinoids to the subjective, behavioral and neurophysiological effects of smoked marijuana. Healthy marijuana users (12 men, 11 women) participated in four sessions. They were randomly assigned to a low or a high Δ9-tetrahydrocannabinol group (THC; 1.8% versus 3.6%). In the four sessions under blinded conditions subjects smoked marijuana cigarettes containing placebo (no active cannabinoids), or cigarettes containing THC with low or high levels of cannabichromene (CBC; 0.1% versus 0.5%) and low or high levels of cannabidiol (CBD; 0.2% versus 1.0%). Dependent measures included subjective reports, measures of cognitive task performance and neurophysiological measures [electroencephalographic (EEG) and event-related potential (ERP)]. Compared to placebo, active THC cigarettes produced expected effects on mood, behavior and brain activity. A decrease in performance, reduction in EEG power and attenuation of ERP components reflecting attentional processes were observed during tests of working memory and episodic memory. Most of these effects were not dose-dependent. Varying the concentrations of CBC and CBD did not change subjects' responses on any of the outcome measures. These findings are consistent with previous studies indicating that THC and its metabolites are the primary active constituents of marijuana. They also suggest that neurophysiological EEG and ERP measures are useful biomarkers of the effects of THC.
aThe San Francisco Brain Research Institute and SAM Technology, USA
bDepartment of Psychiatry, University of Chicago, USA
cNational Center for Natural Products Research, School of Pharmacy, University of Mississippi, USA
Sponsorship: This research was supported by grants from the National Institute on Drug Abuse (DA02812, H.deW. Principal Investigator; DA12840, A.G. Principal Investigator).
Correspondence and requests for reprints to Aaron B. Ilan, SFBRI and SAM Technology, 425 Bush Street, San Francisco, CA 94108, USA
Received 11 May 2005 Accepted as revised 31 July 2005